X=int(input())

now=0
d=0

for i in range(100):
    now+=2
    d+=2
    if now==X:
        break
    now+=2
    d+=2
    if now==X:
        break
    now-=1
    d+=1
    if now==X:
        break
    now-=1
    d+=1
    now+=2
    d+=2
    now-=1
    d+=1
    now-=1
    d+=1
print(d)